EP 3449 describes coextrusion of PVDF with polyurethanes (PU); use of a bonding agent is unnecessary. FR 2 436 676 describes coextrusion of PVDF with polymethyl methacrylate (PMMA) and an acrylonitrile-butadiene-styrene (ABS), the PMMA film being between the PVDF and ABS films. Another example was made with poly(vinyl chloride) (PVC) instead of ABS. EP 450,994 describes an improvement to the above technique, which employs as coextrusion bonding agent the mixture: (a) 27 to 50 parts of PMMA and (b) 73 to 50 parts of a product itself consisting, per 100 parts, of 35 to 50 parts of PVDF and 65 to 50 parts of acrylic or methacrylic elastomer. This improvement increases the adhesiveness of PVDF to ABS.
FR-A-2,457,180 describes polyalkyl methacrylate as an agent for bonding PVDF to incompatible polymers. Among the incompatible polymers are mentioned ABS, polyurethane, polystyrene, polycarbonate, PVC and styrene/acrylic copolymers. However, this bonding agent, in particular PMMA, is not suitable or exhibits a low adhesion towards certain incompatible polymers.
Thus, there is no satisfactory coextrusion bonding agent for adhesively bonding a PVDF film to all the polymers which are incompatible with the latter, in particular polyamide or to a polyamide-based product.